Question

我正在使用JPA和Spring来完成我的数据库任务，我需要在JPA Repo类中有如下所示的连接查询

@Query("SELECT 1 as id, COUNT(bill) as bills, ba.resource, MAX(b.updatedAt) as latestdate FROM Bill b join b.billComp ba where ba.comp.comp = ?1  group by ba.resource")
public List<BillCalc> findByBills(Long comp);

我的实体类如下

@Entity
public class BillCalc {
@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
private Integer id;

@Column(name = "latestdate", nullable = false)
private Date latestdate;

@Column(name = "bills", nullable = false)
private Long bills;

@Column(name = "resource", nullable = false)
private String resource;

我无法为此创建表格，有人可以帮助我使映射工作吗？它给出了一个错误，说不能从Object转换为BillCalc。

我尝试了@SubSelect，但没有参数

Answer 1

将构造函数添加到BillCalc。

BillCalc(Integer id, long bills, String resouce, Date latestdate) {...}

然后使用Select new查询：

SELECT new BillCalc(1, COUNT(bill), ba.resource, MAX(b.updatedAt)) 
    FROM Bill b join b.billComp ba
    WHERE ba.comp.comp = ?1  group by ba.resource")

@参见JSR-000220 Enterprise JavaBeans 3.0 Final Release (persistence)

JPA如何在不创建表的情况下查询数据库

1 个答案: